Flexible interconnect circuits for battery packs

Abstract

Provided are flexible interconnect circuits comprising signal circuit elements. For example, a signal circuit element can be formed from the same metal sheet as a signal trace, thereby being monolithic with the signal circuit element. This integration of signal circuit elements into a flexible interconnect circuit reduces the number of additional operations and components (e.g., attaching external circuit elements). In some examples, a flexible interconnect circuit is used in a battery pack for interconnecting batteries while providing external terminals on the same side of the pack. Specifically, a flexible interconnect circuit comprises an interconnecting conductive layer (for connecting to batteries) and a return conductive layer, both extending between the first and second circuit edges. Each of these conductive layers comprises a corresponding external terminal at the first edge, while these layers are interconnected at the second edge. Otherwise, these layers are isolated from each other between the circuit edges.

1 . A flexible interconnect circuit comprising:
 a first insulator layer;   a second insulator layer, forming a stack with the first insulator layer, wherein:
 the stack comprising a first circuit portion, a second circuit portion, and a middle portion, positioned between the first circuit portion and the second circuit portion along a circuit axis, and 
 the stack comprises multiple slits within the middle portion and extends parallel or at least in part non-parallel to the circuit axis, and 
 the multiple slits enabling the middle portion to change length thereby changing space between the first circuit portion and the second circuit portion; and 
   conductive components positioned between the first insulator layer and the second insulator layer.   
     
     
         2 . The flexible interconnect circuit of  claim 1 , wherein at least one of the conductive components extends between two adjacent ones of the multiple slits. 
     
     
         3 . The flexible interconnect circuit of  claim 1 , wherein each of the multiple slits has a width of less than 5 millimeters. 
     
     
         4 . The flexible interconnect circuit of  claim 1 , wherein each of the multiple slits has a width of less than 2 millimeters. 
     
     
         5 . The flexible interconnect circuit of  claim 1 , wherein each of the multiple slits has a width of less than 1 millimeter. 
     
     
         6 . The flexible interconnect circuit of  claim 1 , wherein the multiple slits have a chevron shape when no tension is applied to the flexible interconnect circuit. 
     
     
         7 . The flexible interconnect circuit of  claim 1 , wherein the multiple slits are parallel to each other when no tension is applied to the flexible interconnect circuit. 
     
     
         8 . The flexible interconnect circuit of  claim 1 , wherein the multiple slits are parallel to the circuit axis. 
     
     
         9 . The flexible interconnect circuit of  claim 1 , wherein each of the multiple slits has an angle of greater than 15° relative to the circuit axis when no tension is applied to the flexible interconnect circuit. 
     
     
         10 . The flexible interconnect circuit of  claim 1 , wherein each of the multiple slits has an angle of greater than 30° relative to the circuit axis when no tension is applied to the flexible interconnect circuit. 
     
     
         11 . The flexible interconnect circuit of  claim 1 , wherein each of the multiple slits has an angle of between 15° and 60° relative to the circuit axis when no tension is applied to the flexible interconnect circuit. 
     
     
         12 . The flexible interconnect circuit of  claim 1 , wherein each of the multiple slits comprises multiple portions that are not colinear with each other and with the circuit axis when no tension is applied to the flexible interconnect circuit. 
     
     
         13 . The flexible interconnect circuit of  claim 1 , wherein an elongation ratio between the middle portion and one of the first circuit portion and the second circuit portion is at least 5. 
     
     
         14 . The flexible interconnect circuit of  claim 1 , wherein an elongation ratio between the middle portion and one of the first circuit portion and the second circuit portion is at least 10. 
     
     
         15 . The flexible interconnect circuit of  claim 1 , wherein an elongation ratio between the middle portion and one of the first circuit portion and the second circuit portion is at least 25. 
     
     
         16 . The flexible interconnect circuit of  claim 1 , wherein one or both of the first insulator layer and the second insulator layer comprise a material selected from the group consisting of polyimide (PI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), ethyl vinyl acetate (EVA), polyethylene (PE), polyvinyl fluoride (PVF), polyamide (PA), and polyvinyl butyral (PVB). 
     
     
         17 . The flexible interconnect circuit of  claim 1 , wherein the conductive components comprise aluminum. 
     
     
         18 . The flexible interconnect circuit of  claim 1 , wherein:
 each of the conductive components comprises a conductive layer and an additional conductive layer,   the conductive layer comprises a contact-forming portion configured to form an external connection,   the additional conductive layer is stacked with and directly interfacing the conductive layer,   both the conductive layer and the additional conductive layer are at least partially positioned between the first insulator layer and the second insulator layer,   the contact-forming portion extends past a boundary of the first insulator layer and the second insulator layer, and   the conductive layer and additional conductive layer are interconnected using a multi-layered connection feature formed by a weld.   
     
     
         19 . The flexible interconnect circuit of  claim 18 , wherein the multi-layered connection feature protrudes through the contact-forming portion of the conductive layer. 
     
     
         20 . The flexible interconnect circuit of  claim 18 , wherein a thickness of the conductive layer is less than a thickness of the additional conductive layer.